In a textile yarn processing machine where yarn is wound into a package at a take-up mechanism, it is necessary when initially threading the yarn to the take-up mechanism to secure the yarn end in some manner in order to begin winding the yarn onto the carrier tube or bobbin tube. Heretofore, the securement of the yarn end has been accomplished in various ways.
For example, one prior method involves the use of a special carrier tube having a slot in one end thereof into which the yarn end is inserted during the thread-up operation. With the yarn end so positioned, the rotation of the carrier tube results in the yarn being wound onto the carrier tube. Another prior technique, as disclosed for example in German Gebrauchsmuster 7,126,191 requires that the yarn end be positioned between the end of the carrier tube and the centering plate upon which the tube is mounted, and frictionally held in place therebetween.
These prior yarn securement techniques have several disadvantages and limitations. Not only are they unsuited for automated thread-up operations, but in manual operations they prolong the thread-up procedure since it is necessary for the operator either to search for the slot on the carrier tube where the yarn is to be inserted, or to manually shift the carrier tube axially away from the centering plate in order to position the yarn therebetween. Additionally, after extended use, the end faces of the yarn carrier tubes tend to become damaged, and it is then no longer possible to insure reliable securement of the yarn end.
In German Offenlegungsschrift No. 2,312,609, a yarn securement arrangement is disclosed wherein the centering plate is mounted so as to be axially displaceable with respect to a clamping plate to expose a gap therebetween into which a yarn may be positioned and then clamped in place. When the yarn package has been fully formed and ready for removal from the take-up mechanism, the centering plate is again moved axially away from the clamping plate so that the yarn end is released. A somewhat similar arrangement for clamping the yarn end has also been disclosed in German Offenlegungsschrift No. 2,332,727.
These arrangements, like those noted earlier, are not suited for automated thread-up operations. Also, the arrangement disclosed in German Offenlegungsschrift No. 2,312,609 is relatively expensive to construct because of the necessary relative movements between the centering plate and the clamping plate.
In German Patent Specification No. 949,900, there is disclosed a winding mechanism for cables wherein the securement of the cable is intended to be accomplished by providing a circumferential groove in the carrier tube itself. However, unless the cable is pulled securely into the groove, the cable may slide out relatively easily when winding begins.
In Swiss Pat. No. 450,855, there is disclosed an arrangement for securing the end of a yarn for winding on a carrier tube or bobbin in which there is a groove or channel in which the yarn is inserted, and wherein at least one projection is provided projecting into the groove for wedging and holding the yarn in place. However, in spite of this projection, there exists a risk that the yarn may slip out of the groove when winding begins unless the yarn is carefully and securely inserted initially.
An arrangement which is much simpler than the prior devices previously described, and which is intended for both automatic and manual securement of the yarn end, is disclosed in commonly-owned German Patent Specification No. 2,536,477. In this device, the centering plate has a circumferentially extending yarn securement channel which is provided with opposing pairs of wedge shaped grooves in the opposing side walls of the channel for wedging or jamming a yarn therebetween. The grooves on one side wall of the channel extend in the direction of rotation of the centering disc and the opposing grooves on the other side of the channel extend opposite the direction of rotation. The side wall closest to the carrier tube is provided in the zone of each set of wedge shaped grooves with an undercut protrusion or nose facing in the direction of rotation of the centering plate. The principal function of the protrusion is to facilitate the transfer of the yarn from the yarn securement channel to the carrier tube when winding begins.